Subject: Re: [vserver] Possible Hashify Corruption - Update 2
From: Gordan Bobic <gordan@bobich.net>
Date: Wed, 20 Oct 2010 19:41:10 +0100

On 20/10/2010 18:39, Ed W wrote:
> On 20/10/2010 15:02, Gordan Bobic wrote:
>> I have just tested this with a new kernel. And the issue doesn't arise
>> with 2.6.35.7-vs2.3.0.36.33! So it is definitely a kernel bug, most
>> likely in ext4.
>
> Cripes. That's rather scary...

Tell me about it! I'm guessing it will affect anything that works with 
hard-links on ext4 in that kernel. I'd rather like to know how that got 
through testing without being picked up. At the very least, that kernel 
should have been tagged with a big fat warning message.

> Well done for tracing it down - hope those filesystems are replaceable..?

I was just about to put the system into production so there was no data 
on it yet. The only vaguely valuable thing was the configs (a few hours 
work at most, I probably spent more time debugging the issue when it all 
went wrong), and those survived since they didn't get hashified. :)

So not much harm done, but it could have been much worse. Since it 
doesn't become apparent until after a reboot due to the healthy versions 
sticking in caches as unflushable, that data could have been getting 
corrupted for days before the machine ran out of RAM and died. Only then 
would the corruption have become apparent.

Gordan